Colloidal diaphragm adapted for use in electrolytic apparatus for the manufacture ofhydrogen and oxygen



Patented Dec. 15, 1931 UNITED STATES- PATENT OFFICE- GEORGE FRANCOISJ'AUBEBT, OF PARIS, FRANCE COLLOIDAL DIAPHRAGM ADAPTED FOR USE INELECTROLYTIC APPARATUS FOR THE IANUEACTURE OF HYDROGEN .AND OXYGEN NoDrawing. Application filed November 22,1927, Serial No. 235,118, and inFrance December 1, 1926 I have already shown that it was feasible toemploy as a diaphragm for the perfect separation of oxygen and hydro engas at the time of their formation in tie electrolytic tank, a wiregauze member, a woven fabric, for instance of asbestos, or perforatedsheet metal, but on the express condition that the cross-section of eachof the innumerable orifices in this diaphragm shall be so small that thesurface tension of the liquid contained in each of the minute orificesand formingthesurface of separation between the two fluids (such asliquid, gas or emulsion), contained in the anode and the cathodechambers, shall exceed the counter-pressure prevailing respectively inthese two chambers, Which counter-pressure tends constantly to cause themixing of the oxygen and hydrogen gases, thus forming a dangerousexplosive 2o mixture.

If the above-mentioned conditions are strictly observed, a completeseparation will be effected, and the oxygen and hydrogen.

gases will each be obtained in a very pure state. i

However, the manufacture of wire gauze, fabrics, or erforated sheetmetal, having the necessary egree of fineness to comply with the saidconditions, becomes a most expensive matter. In fact, when the holes areof a small size, their number will increase for a given surface, and thecost of manufacture is thus augmented.

A great advantage, and a considerable progress in manufacture, would beobtained by the use of sheet steel having larger holes, or of wire gauzesheets of the current sizes which are found in the market and inwhichthe holes are much lar er than what theory prescribes. This would offera great saving in cost, and would represent a considerable improvementin my said above process. It was however necessary to means forrevent-ing the anode and the'cathode gases rom passing through theselarger holes.

I have obtained this result by means of a colloidal diaphragm, the subect matter of the present invention, which diaphragm is so to speaksuperposed upon the diaphragm mentioned hereabove.

- I have observed that by the use of a diaphragm' consisting ofperforated sheet metal or wire gauze, or even of a strong textilefabric, whose holes are too large to assure a sufficient separationbetween the anode and the cathode gases in the nascent state, it issimply necessary to coat this diaphragm with the hydrogel of a colloidalsubstance'which is unafi'ected by the electrolyte in the conditions ofthe operation, in order to-obtain at once a perfect separation of thegases, and without any appreciable reduction of the electric efficiencyof the apparatus.

The term hydrogel refers. to all organic or inorganic bodies in a stateof fine suspension in water or in an electrolyte or other solvent, thesize of its parti les being between 1/ 1,000 and 1/ 1,000,000millimeters diameter, which suspended particlw have the property ofbeing transportable in the electric field by the action of the current.

The said colloidal diaphragm according to my invention can be variouslymanufactured as follows.

L The imperfect diaphragm, such as steef wire gauze N o. 30 to 50, iscoated by a spatula with a hydrogel paste already prepared, for instanceaccording to the list given below.

2.-The hydrogel is formed'in the holes of the diaphragm, i. e. thepreparation is carried out in situ. Considering for example the wiregauze above mentioned, this is immer'sed in a soluble salt which isdissolved to the proper strength, and then without drying the diaphragmthus'moistened (each l mersed in a solution of another substance,

thus forming the hydrogel by double decomposition or coagulation, or thelike.

As an example, I immerse a wire gauze sheet in an aqueous solution ofmagnesium sulphate or chloride, and then in an aqueuos solution ofsilicate of soda. There is at once formed in the holes of the wire gauzea hydrogel of magnesium silicate, otherwise known as colloidal asbestos,which is ex tremely porous and forms an excellent diaphra m, thusassuring the perfect separation etween the hydrogen and oxygen.

3.'-I may proceed in the following manner, making use of the fact thatthe colloidal substances will serve as electrolytes, taking part in thephenomenon of electrolysis and moving in the electric field.

For this purpose I place in an electrolytic tank of any type, the twoelectrodes, positive and negative, which are separated by an imperfectdiaphragm, such as a No. 3050 steel wire gauze sheet. I then add theelectrolytic bath (an aqueous solution of caustic soda or potash of 15to 20 percent strength) holding in suspension the suitable hydrogelwhich ma be organic or inorganic, all that is require being thatit willbe transported by the current, which gradually fixes it upon thediaphragm by an action of adsorption. It is obvious that this hydrogenmust not be attacked by the electrolyteto any great degree, in theconditions of temperature and concentration in which the operation isperformed with the said electrolyte consisting of water represented bythe alkaline solution.

The best results are furnished by the following hydrogels whether or nicor inorganic, these being given sole y by way of example and withoutlimitation-silicates of magnesia, silicates of iron, the kaolins, theferric hydrates, yellow ochre natural or artificial, the limonites, theclays, hosphates of magnesia and of alumina car on in the form ofraphite, carbon from blood, india rubber, t e hydrates ofthe alkalineearths or those ofthe series of rare earths, the flocculent metals suchas copper and nickel, and the like. Wherever the use of the phrasecolloid impervious to an attack by alkaline solution or alkali, is madein the specification andclaims, it is intended to include any of theabove substances.

If the electrolyte consists of a solution of sodium or potassiumcarbonate, I obtain a good dia hragm b the use of a hydrogel of hydrocaronate of magnesia.

'The quantities of the said hydrogels to be added to the electrolyte aresmall, as a general rule. When the apparatus is put in operation, I adda quantity which is about 5 to 10 per cent-estimated as dry substanceforeach liter of electrolyte.

. As soon as the hydrogel is fixed by electric transportation into theholes of the wire gauze in which it forms a gelatinous spongy substancepierced with extremely fine holes, the bath becomes clearer, due to theabsence of the amount of the said substance which has been fixed uponthe diaphragm, and-the gases are then perfectly pure.

I add at intervals a certain quantity of hydrogel, in case the portionfixed on the wire gauze should be accidentally detached, and shrogldfall to the bottom of the electrolytic ta' Should the electrolyticapparatus be taken apart, or its use discontinued for a long time, thediaphragm should not be dried, since it would lose its effectiveness; itshould be simply washed with water to remove the eyectrolyte, and isthen dipped in a 50 per cent glycerine solution and allowed to drain.

Obviously, the three methods of preparation herein specified by way ofexample may be combined together, or like methods may be devised withequal facility.

My said diaphragm according to the invention may be employed equallywell with electrolytic apparatus of the tank type utilizing a diaphragm,or with electrolytic apparatus of the plate type represented by filterpresses. My said method is advantageous for these latter, as I mayemploy if necessary a very inferior grade of asbestos cloth, with aconsequent reduction in cost, whereas such material could not be used inthe absence of the said layer of colloidal hydrogel. I

What I claim is 1. A process for the manufacture of diaphragms forelectrolytic cells which comprises passing a current through anelectrolyte containing a colloid impervious to an alkaline solution anddepositing the colloid on a metal diaphragm during the electrolysis ofthe electrolyte while fixing the colloid on said metal diaphragm andmaintaining the fiow of the current through the electrolyte.

2. A process for the manufacture of diaphragms for electrolytic cellswhich are permeable to the electrolyte but impermeable to the gaseousproducts evolved by the electrolysis which comprises forming a metaldiaphragm, surrounding the diaphragm with an electrolyte solutioncontaining a colloid impervious to attack by the electrolyte solution,passing an electric current through the electrolyte and causingdisassociation of the elements of the electrolyte while causing thecolloid to be deposited on the diaphragm so that hydrogen and oxygenwhich are bein evolved from the electrolyte will be separate from eachother when the colloid has completelX covered the diaphragm.

3. process for the manufacture of diaphragms for electrolytic cellswhich are permeable to the electrolyte but impermeable to the gaseousproducts evolved by the electrolysis which comprises forming a metaldiaphragm, surrounding the diaphragm with an electrolyte solutioncontaining a colloid impervious to attack by the electrolyte solution,passing an electric current through the electrolyte and causingdisassociation of the elements of the electrolyte while causing the.

colloid to be deposited on the diaphra so that hydrogen and oxygen whichare a ing evolved from the electrolyte will beseparated from each otherwhen the colloid has completely covered the diaphragm,

In testimony whereof I have hereunto set my hand.

GEORGE FRANCOIS JAUBERT.

